The present invention relates to a process for removing volatile, water insoluble substances from solid substances, and more particularly to a process for removing halogenated hydrocarbons from synthetic foams.
Synthetic foams, depending on their use, contain various amounts of halogenated hydrocarbons (hereinafter "FCH"). FCHs are, for example, known in Germany under the trademarks Frigen or Freon. Depending on the manufacturer, the Frigens or Freons of the type R11 and R12 are used in differing weight ratios. The major portion, however, is usually R11. A preferred application of synthetic foams is in the insulation of cooling devices, where a polyurethane foam (PUR) is used having a total content of Frigen or Freon of about 15%.
In the processing of used refrigerators, the pores of the synthetic foam are opened by comminution, compaction or a combination of both procedures for the purpose of FCH extraction. Care must be taken for reasons of environmental protection that the FCH is not released into the atmosphere, but recovered.
In a known process of the art, the FCH is released into process air which acts as a carrier medium. The FCH is then recovered by a low-temperature treatment of the process air. Due to the low vapor pressure of R11 (boiling point of 23.8.degree. C.), however, this temperature treatment is difficult because temperatures in the order of -60.degree. C. must be attained to achieve a good separation. The occurrence of water condensation and ice formation beforehand make the realization of this process difficult. This is even more so the case in the recovery of R12 due to an even lower boiling point of -29.8.degree. C.